Thought I would install Mate and give it a go but when attempting to install I get a slot conflict I can't seem to sort out

Code:

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-libs/glib:2

(dev-libs/glib-2.36.4::gentoo, ebuild scheduled for merge) pulled in by
>=dev-libs/glib-2.35.2:2 required by (gnome-base/dconf-0.16.1::gentoo, ebuild scheduled for merge)
(and 1 more with the same problem)

(dev-libs/glib-2.32.4-r1::gentoo, installed) pulled in by
<dev-libs/glib-2.33:2 required by (dev-libs/gobject-introspection-1.32.1::gentoo, installed)

After updating dev-libs/gobject-introspection than x11-libs/gdk-pixbuf with the introspection USE FLAG required by the mate ebuild breaks with a variation of the BUG # 463884 and can't be installed causing emerge to refuse to continue due to unsatisfied dependencies.

While I will continue to work on these problems and hopefully sort it all out, I was hoping somebody with a lot more knowledge than me with portage, ebuilds and dependencies could point me in the right direction.

Accept keywords for >=dev-lang/vala-0.20.0 and unmask it, then try again.

Thanks I actually sorted it out and have MATE installed though I haven't started it up just yet.

STEP 1.
It seems a lot of packages have the USE FLAG introspection set by default and because I couldn't build x11-libs/gdk-pixbuf with the newer gobject-introspection I added -introspection to my make.conf and added =x11-libs/gdk-pixbuf-2.26.4 introspection, >=mate-base/mate-menus-1.6.0 introspection, =x11-libs/pango-1.30.1 introspection, =x11-libs/gtk+-2.24.17 introspection, =dev-libs/atk-2.6.0 introspection to /etc/portage/package.use and ran an NewUse update using the older version of gobject-introspection first to satisfy the mate ebuilds.

Not sure this was this wisest of choices, however I will attempt to revert back to the default introspection USE setup.

STEP 2.
Next I added =dev-lang/vala-0.20.1 and =dev-libs/vala-common-0.20.1(required by vala-0.20.1 to /etc/portage/package.keywords and updated vala. This process auto uninstalled the older version of vala already installed.

STEP 3.
Next I added =dev-libs/gobject-introspection-1.36.0, =dev-libs/gobject-introspection-common-1.36.0(required by gobject-introspection) and =dev-libs/glib-2.36.4 to /etc/portage/package.keywords and updated gobject-introspection which also updated gobject-introspection-common and glib.

STEP 4.
Install MATE from the layman overlay. Which finally completed without errors.

STEP 5. To Do Yet
Revert back to the default introspection USE setup and check for system breakage.

I installed Xfce about a year ago knowing Gnome2 was dead. I tried Gnome3 and its different flavors both installing it on one of my Gentoo machines and several other distros in VirtualBox. No matter how hard I tried I just can't stand it and I have been a Gnome user since the Mandrake 6 days. Xfce is great but I have had to install a lot of gnome2 apps to get the complete system I like and when Gnome3 goes stable Gentoo will drop Gnome2, as it should be and I will loose most of my Xfce unless I want to maintain my own ebuilds which I don't. I think MATE will a viable fully functioning alternative DE.

Completing STEP 5.
Removing -introspection from my make.conf and running a world update caused a vala blocker immediately and I had to unmask =net-libs/gssdp-0.14.3 to get around that. Than librsvg failed in reference to gdk-pixbuf-2.26.4 which failed again. Unmasking =x11-libs/gdk-pixbuf-2.26.5 finally sorted it all out.

Couldn't start MATE from the console (I don't use a login manager, never have) and had to create a ~. xinitrc file with